Sulfur oxide and nitrogen oxide in flue gas are main precursor substances of acid rain. The acid rain pollution in China is in a severe situation. In every year, economic loss due to the acid rain and sulfur dioxide is up to hundreds of billion yuan throughout the country. In addition, the sulfur dioxide and nitrogen dioxide are also main pollutants participated in air quality evaluation. As a result, the control of emission of the sulfur oxide and the nitrogen oxide generated in a combustion process to an atmospheric environment has a very important practical significance.
A widely-used flue gas desulfurization and denitrification technology mainly is a wet-process limestone-gypsum flue gas desulfurization technology and an ammonia selective catalytic reduction technology. The above technical methods can implement the removal of the sulfur oxide and the nitrogen oxide in the flue gas respectively but fail to implement simultaneous desulfurization and denitrification on the flue gas. A traditional wet-process flue gas purification technology, such as limestone-gypsum flue gas desulfurization technology and ammonia flue gas desulfurization technology, cannot implement the simultaneous desulfurization and denitrification on the flue gas, which lies in a fact that 90% or more of nitrogen oxides in the flue gas are NO difficult to be dissolved and absorbed. Therefore, in order to realize an objective of the simultaneous desulfurization and denitrification on the flue gas, converting the NO in the flue gas into a form to be dissolved and absorbed easily is a key to solve the problem. CN101940871B discloses a “simultaneous desulfurization and denitrification system based on photochemical advanced oxidation”. The method mainly decomposes a hydrogen peroxide by using ultraviolet excitation; and a strong oxidizing hydroxyl radical (⋅OH) is generated to contact with flue gas in a spray tower to take place a gas-liquid absorption reaction, thus oxidatively removing NOx and SO2 in the flue gas. CN102166471B discloses an “integrated flue gas purification system based on heterogeneous Photo-Fenton”. The method generates a strong oxidizing hydroxyl radical (⋅OH) by using the heterogeneous Photo-Fenton to oxidize SO2, NO and the like in flue gas into H2SO4 and HNO3, thus oxidatively removing the SO2 and NO in the flue gas. CN202096874U discloses a “flue gas purification device based on advanced oxidation combined wet-process cleaning”. The utility model mixes ozone generated by an ozone generator with flue gas, and inputs a mixture to a reactor having an ultraviolet tube; and under radiation and excitation of ultraviolet light, a strong oxidizing hydroxyl radical (⋅OH) is generated, and is oxidized with SO2, insoluble NO and the like in the flue gas into a gaseous product having high solubleness, to enter a gas-liquid absorption tower to be absorbed by water for removal. CN103638796B discloses a “desulfurization-denitrification-demercuration system based on photoactivated ammonium persulfate”. Flue gas emitted from a boiler or a kiln is subject to dedusting and temperature regulation to enter a photochemical reactor on a gas flue; and an ammonium persulfate solution from a liquid spray system is sprayed to the photochemical reactor in a mist form. An ultraviolet lamp in the photochemical reactor emits ultraviolet light to catalytically decompose the ammonium persulfate and release a strong oxidizing sulfate free radical (SO4.−) to remove SO2, NOx and mercury in the flue gas oxidatively and simultaneously. CN104043325B discloses a “method and device for purifying flue gas with ozone activated persulfate”. According to the method, the ozone in the flue gas contacts with persulfate in a solution in a bubbling-spraying two-stage reactor to generate strong oxidizing sulfate free radical and hydroxyl free radical to oxidatively remove SO2, NOx and other pollutants in the flue gas.